Safe Body Current

Factors that determine the severity of the electric shock effects are:

1. The duration of the electrical shock

2. Magnitude of the current

3. Magnitude of the voltage

4. Frequency of the current

5. Path through the body

The human body's response changes between an individual's skin contact and electrical path. For example, a 3-milliam-pere shock for 1 millisecond through the heart or brain can cause death or paralysis for some individuals. Researchers have used a large number of subjects to arrive at average values and safety levels for the most susceptible. Table D-l presents some typical responses to various levels of electrical shock. These responses were derived by Dalziel and discussed in "Effects of Elec tric Shock on Man" (Ref D-2). Table D-l provides a basis for electrical safety on land, but NOT safe operating levels for divers in water.

Figure D-l shows safe body current levels for divers as adopted by the AODC and BUMED, and defines the maximum current/time relationships to which a diver may be exposed. Based on research and uncertainties relating to underwater use, the values used for worst case, limb-to-limb contact resistance on a diver in the water are:

• 750 ohms for voltages up to 50 volts

• 500 ohms for voltages over 50 volts

• 100 ohms at any voltage for possibility of a front to back of the chest contact path

60765 Chicago Industrial Wiring

Table D-l. Electrical Safety on Land

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